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United States Patent |
5,325,409
|
Yaginuma
|
June 28, 1994
|
Fuel rod guiding apparatus and method therefor
Abstract
A guiding apparatus and a method are presented for efficiently guiding and
loading fuel rods into a fuel assembly without introducing surface damage
to the fuel rod. The apparatus simultaneously loads a row of fuel rods
into the grid cells of the grids using the guiding device, disposed at the
entry side of each grid. The guiding device includes a comb-shaped section
and a freely detachably engaged bottom side wall plate, forming a
plurality of guiding spaces to superimpose on the plurality of grid cells
requiring fuel rods. The guiding device is provided with protective
guiding strips which are inserted into the grid cells prior to inserting
the fuel rods so as to protect the fuel rod surface from being scratched
by the springs and dimples provided. The method of fuel rod insertion
using the apparatus is as follows. The guiding spaces formed by the
comb-shaped section and the bottom side wall plate are placed adjacent to
the opening end surface of a row of grid cells. After the fuel rods are
inserted, the comb-shaped section is separated from the bottom side wall
plate, and is raised to the next row of horizontal grid cells. The
detached bottom side wall plate located below the fuel rods is rotated
away and then raised above the fuel rods to the next row of horizontal
grid cells. The bottom side wall plate is now rotated back and reengaged
with the comb-shaped section and the loading process is repeated for the
row above.
Inventors:
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Yaginuma; Yoshitaka (Tohkai, JP)
|
Assignee:
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Mitsubishi Nuclear Fuel Co. (Tokyo, JP)
|
Appl. No.:
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043733 |
Filed:
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April 7, 1993 |
Foreign Application Priority Data
Current U.S. Class: |
376/261 |
Intern'l Class: |
G21C 021/00 |
Field of Search: |
376/261,260
29/723,906
|
References Cited
U.S. Patent Documents
4723359 | Feb., 1988 | Blissell et al. | 376/261.
|
4731219 | Mar., 1988 | Beneck et al. | 376/261.
|
4740351 | Apr., 1988 | Katsumizu et al. | 376/261.
|
4793962 | Dec., 1988 | Tsitsichvili | 376/261.
|
4981640 | Jan., 1991 | Beneck et al. | 376/261.
|
5028382 | Jul., 1991 | King, Jr. et al. | 376/261.
|
Primary Examiner: Wasil; Daniel D.
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt
Claims
What is claimed is:
1. A fuel rod guiding apparatus for simultaneously guiding a plurality of
fuel rods into a plurality of grid cells formed in a supporting grid of a
fuel assembly, so as not to introduce surface damage on said fuel rods
during insertion, wherein said plurality of grid cells are formed by a
latticed network of one set of straps and another set of straps orthognal
to said one set of straps, each strap provided with a plurality of springs
and dimples; said apparatus comprising:
(a) guiding means disposed on the entry side of said supporting grid for
guiding said fuel rods into said grid cells; and
(b) driving means for driving said guiding means;
said guiding means comprising:
(c) a comb-shaped section having an elongated part extending coplanarly to
a strap of one set of straps, and a plurality of dividing parts extending
from said elongated part, each of said dividing parts being extended
coplanarly to each strap of another set of straps;
(d) side wall plate disposed opposite to said elongated part of said
comb-shaped section, and freely separably engaged with said dividing part
of said comb-shaped section thereby forming guiding spaces for insertion
of said fuel rods to correspond with said plurality of grid cells;
(e) a guiding strip disposed on each wall around each guiding space of said
guiding spaces, extending in the exit direction of said fuel rod so as to
contact a cylindrical surface of said fuel rod inserted into said grid
cell;
wherein said driving means drives:
said comb-shaped section and said side wall plate as a unit towards and
away from an opening end surface of said gird;
said comb-shaped section and said side wall plate towards and away from one
another; and
said comb-shaped section and said side wall plate so as to engage with and
disengage from each other.
2. A guiding apparatus as claimed in claim 1, wherein a plane in which said
plurality of fuel rods are arranged for simultaneous insertion into said
supporting grid is parallel to said one set of straps.
3. A guiding apparatus as claimed in claim 1, wherein said one set of
straps are aligned in a horizontal direction.
4. A guiding apparatus as claimed in claim 2, wherein said one set of
straps are aligned in a horizontal direction.
5. A guiding apparatus as claimed in claim 1, wherein said side wall plate
is supported freely rotatably at one end, and said driving means rotate
said side wall plate pivoted at said one end.
6. A guiding apparatus as claimed in claim 2, wherein said side wall plate
is supported freely rotatably at one end, and said driving means rotate
said side wall plate pivoted at said one end.
7. A guiding apparatus as claimed in claim 3, wherein said side wall plate
is supported freely rotatably at one end, and said driving means rotate
said side wall plate pivoted at said one end.
8. A guiding apparatus as claimed in claim 4, wherein said side wall plate
is supported freely rotatably at one end, and said driving means rotate
said side wall plate pivoted at said one end.
9. A method of guiding and inserting a plurality of fuel rods
simultaneously into a fuel assembly from an entry side of said assembly
comprising a plurality of grids having a plurality of grid cells formed by
one set of straps and another set of straps orthognal to said one set of
straps wherein all the straps have springs and dimples formed thereon,
with using guiding means comprising:
a comb-shaped section having an elongated part extending parallel to one
set of straps, and a plurality of dividing parts extending from said
elongated part in parallel to a plurality of another set of straps
orthognal to said one set of straps;
side wall plate disposed horizontally, and freely separably engaged with
said comb-shaped section thereby forming guiding spaces for insertion of
said fuel rods to correspond with said plurality of grid cells; and
a guiding strip disposed on each wall around each guiding space of said
guiding space, extending in the exit direction of said fuel rods so as to
contact a cylindrical surface of said fuel rod disposed in said grid cell;
said method comprising the steps of:
(A) forming guiding spaces to correspond with said grid cells by engaging
said side wall plate with said comb-shaped section, and disposing said
guiding spaces adjacent to an opening end surface of said grid;
(B) inserting said guiding strips into a horizontal row of grid cells by
advancing said guiding mechanism in the direction of the fuel rods;
(C) inserting a plurality of fuel rods into the guiding spaces formed by
said guiding mechanism;
(D) withdrawing said guiding mechanism in the direction of the fuel rods so
as to remove said guiding strips from the row of grid cells;
(E) raising said comb-shaped section of said guiding mechanism in parallel
with said opening end surface of said grid, and in a parallel orientation
to the side wall plate;
(F) rotating to move said side wall plate of said guiding mechanism to a
region free from mechanical interference with the fuel rods;
(G) transferring said comb-shaped section and said side wall plate to
another horizontal row, and repeating the steps A to G until the required
grid cells of all the grids in said fuel assembly are filled with fuel
rods.
10. A method as claimed in claim 9, wherein a plane in which said plurality
of fuel rods are arranged for simultaneous insertion into said supporting
grid is parallel to said one set of straps.
11. A method as claimed in claim 9, wherein said one set of straps are
aligned in a horizontal direction.
12. A method as claimed in claim 10, wherein said one set of straps are
aligned in a horizontal direction.
13. A method as claimed in claim 9, wherein said side wall plate is
supported freely rotatably at one end, and said driving means rotate said
side wall plate pivoted at said one end.
14. A method as claimed in claim 10, wherein said side wall plate is
supported freely rotatably at one end, and said driving means rotate said
side wall plate pivoted at said one end.
15. A method as claimed in claim 11, wherein said side wall plate is
supported freely rotatably at one end, and said driving means rotate said
side wall plate pivoted at said one end.
16. A method as claimed in claim 12, wherein said side wall plate is
supported freely rotatably at one end, and said driving means rotate said
side wall plate pivoted at said one end.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an assembling apparatus and an assembling
method of a nuclear fuel assembly, and more specifically to a guiding
apparatus which enables the insertion of fuel rods to be carried out
efficiently and free of surface scratches.
2. Technical Background of the Invention
In general, pressurized light water nuclear reactors utilize a type of fuel
assembly in which a number of fuel rods are arranged horizontally at
regular intervals. The fuel assembly comprises an upper nozzle, a lower
nozzle and a plurality of fuel rod supporting grids (shortened to grids
henceforth), made of thin metal straps intersecting orthognally to form
grid cells. Fuel rod-guide pipes and instrumentation pipes are inserted
into the grid cells, and are fixed to the grids and also to the upper and
the lower nozzles at the ends. Fuel rods are also inserted into and are
supported elastically in the grid cells by means of springs formed inside
the grid cells.
When assembling such a fuel assembly, there is a danger of introducing
scratches on the surface of the fuel rods if the rods are inserted into
the grid cells as they are, because of the presence of the fuel rod
supporting springs and dimples which are formed inside the grid cells. To
prevent such a surface damage to the fuel rods, the springs must
temporarily be deactivated while the fuel rods are being inserted into the
grid cells. However, the technology to successively deactivate a large
number of springs formed on each strap in the assembly required a high
precision in the tooling and advanced drive-control technology.
In view of such problems in the existing technology, there have been, prior
to the present invention, alternative proposed techniques, such as those
presented below.
An assembling method is known, in which surface scratches are prevented by
applying a cylindrical protective sleeve on the fuel rod over its entire
external surface before its insertion into the grid cells, and removing
the sleeve after the insertion is completed. (Japanese Patent Application,
First Publication, S53(1978)-11294)
Another approach is to insert a slitted cylindrical jig in the grid cell
beforehand, and after placing the fuel rod in the jig, the jig is moved
into the assembly with the fuel rod, and the jig is removed with the use
of the slit. (Japanese Patent Application, First Publication,
S60(1985)-50490)
Another method is to arrange a plurality of such slit tools in a line along
the grid cells, and to insert a line of fuels rods all at once. (Japanese
Patent Application, First Publication, S60(1985)-67891)
Yet another method is to insert a cylindrical plastic sheet into the grid
cell prior to inserted a fuel rod in the plastic sheet. (Japanese Patent
Application, First Publication, S60(1985)-181680)
Yet another method is to prepare a rattan type support made of a series of
thin plastic strips, and arrange the supports in accord with the grid
cells prior to inserting the fuel rods into the support. (Japanese Patent
Application, First Publication, S60(1985)-213889)
Such method which utilize various protective covers between the grid cells
and the fuel rods are effective in preventing the formation of surface
scratches on the fuel rods, but none of them provided for an automated
facility for insertion of a plurality of fuel rods efficiently. Therefore,
the operation was labor-intensive, and a need existed to reduce the labor
content associated with such operations.
SUMMARY OF THE INVENTION
The objective of the present invention is to present an apparatus and a
method for efficiently loading the fuel rods automatically into a fuel
assembly without introducing surface scratches on the cylindrical surface
of the fuel rods.
The guiding apparatus of the present invention is present for
simultaneously guiding a plurality of fuel rods into a supporting grid
cell formed in a plurality of grids of a fuel assembly, so as not to
introduce surface damage on the fuel rods during insertion, wherein the
plurality of grid cells are formed by a latticed network of one set of
straps and another set of straps orthogonal to the one set of straps, each
strap provided with a plurality of springs and dimples; the apparatus
comprising:
(a) guiding means disposed on the entry side of said supporting grid for
guiding the fuel rods into the grid cells; and
(b) driving means for driving the guiding means;
the guiding means comprising:
(c) a comb-shaped section having an elongated part extending coplanarly to
a strap of one set of straps, and a plurality of dividing parts extending
from the elongated part, each of the dividing parts being extended
coplanarly to each strap of another set of straps;
(d) side wall plate disposed opposite to the elongated part of the
comb-shaped section and freely separably engaged with the dividing parts
of the comb-shaped section thereby forming guiding spaces for insertion of
the fuel rods to correspond with the plurality of grid cells;
(e) a guiding .strip disposed on each wall of said guiding space, extending
in the exit direction of the fuel rods so as to contact a cylindrical
surface of the fuel rod inserted into the grid cell;
wherein the driving means drives:
the comb-shaped section and the side wall plate as a unit towards and away
from an opening end surface of the gird;
the comb-shaped section and the side wall plate towards and-away from one
another; and
the comb-shaped section and the side wall plate so as to engage with and
disengage from each other.
The apparatus constructed as presented above is disposed at the entry side
of the opening end surface of each of the grids, and is used to load a
required number of fuel rods laterally arranged in a row into the grid
cells of all the grids of the assembly.
A method is presented using the apparatus described above of guiding and
inserting a plurality of fuel rods simultaneously into a fuel assembly
from an entry side of the assembly comprising a plurality of grids having
a plurality of grid cells formed by one set of straps and another set of
straps orthognal to the one set of straps wherein all the straps have
springs and dimples formed thereon, with using guiding means comprising:
a comb-shaped section having an elongated part extending parallel to one
set of straps, and a plurality of dividing parts extending from the
elongated part in parallel to a plurality of another set of straps
orthognal to the one set of straps;
side wall plate disposed horizontally, and freely separably engaged with
the comb-shaped section thereby forming guiding spaces for insertion of
the fuel rods to correspond with the plurality of grid cells; and
a guiding strip disposed on each wall of said guiding space, extending in
the exit direction of said fuel rods so as to contact a cylindrical
surface of the fuel rod disposed in the grid cell;
the method comprising the steps of:
(A) forming guiding spaces to correspond with the grid cells by engaging
the side wall plate with the comb-shaped section, and disposing the
guiding spaces adjacent to an opening end surface of the grid;
(B) inserting the guiding strips into a horizontal row of grid cells by
advancing the guiding mechanism in the direction of the fuel rods;
(C) inserting a plurality of fuel rods into the guiding spaces formed by
the guiding mechanism;
(D) withdrawing the guiding mechanism in the direction of the fuel rods so
as to remove the guiding strips from the row of grid cells;
(E) raising the comb-shaped section of the guiding mechanism in parallel
with the opening end surface of the grid, and in a parallel orientation to
the side wall plate;
(F) rotating to move the side wall plate of the guiding mechanism to a
region free from mechanical interference with the fuel rods;
(G) transferring the comb-shaped section and the side wall plate to another
horizontal row, and repeating the steps A to G until the required grid
cells of all the grids in the fuel assembly are filled with fuel rods.
In the above method of guiding, guiding spaces to correspond with the
required grid cells into which the fuel rods are to be inserted are
generated when the comb-shaped section is engaged with the side wall
plate.
With the use of the driving device, the guiding apparatus is moved towards
the exit side to position it close to the entry side of the opening end
surface of each of the grids. In this condition, the straps provided on
the guiding apparatus are inserted into the grid cells, and slides over
the springs/dimples provided on the straps. When the fuel rods are
inserted into the grid cells, the fuel rods slide over the guiding strips
and the springs and dimples do not come into direct contact with the
cylindrical surface of the fuel rods. Because the guiding strips are in a
sheet form intervening between the fuel rods and the springs/dimples, the
fuel rods enter the grid cells smoothly without introducing any scratches
on the surface.
After the fuel rods are inserted completely into the assembly, the guiding
apparatus is withdrawn by moving it away from the entry side, then the
guiding strips clamped between the fuel rods and the springs/dimples are
also withdrawn from the grid cells.
Subsequently, the comb-shaped section is separated from the side wall plate
which is rotated away by pivoting around one end of the side wall plate,
and the comb-shaped section is independently moved vertically to the next
row of grid cells. The side wall plate is then raised to the next row of
grid cells, and reengaged with the comb-shaped section. Thus the guiding
apparatus has been moved from one of grid cells to the next row of grid
cells situated above the previous row of grid cells. This process is
repeated for the remaining grid cells in the grid until all the required
grid cells are filled with the fuel rods.
According to the method described above, the fuel rods are inserted
smoothly into the grid cells with the intervening strips between the fuel
rods and the springs/dimples, thus positively preventing the introduction
of scratches on the surface of the fuel rods. There is no need for
deactivating the springs successively for the girds in the assembly, and a
certain pressure is all that is needed initially to insert the fuel rods.
Furthermore, for each row of grid cells, the superimposing guiding spaces
are generated automatically, and a row of fuel rods are inserted
simultaneously into the grid cells, thus improving the efficiency of
assembling operation of the fuel assembly.
BRIEF EXPLANATION OF THE DRAWINGS
FIG. 1 is a front view of the fuel rod guiding apparatus of the present
invention seen from the direction of insertion into the grid.
FIG. 2 is a side view of the fuel rod guiding mechanism of the present
invention.
FIG. 3 is a schematic view of the fuel rods arranged on the fuel rod base
for insertion into the grid cells.
FIG. 4 is a perspective view showing the structure of the fuel rod guiding
apparatus of the present invention.
FIG. 5 is a partial cut away top view of the fuel rods inserted in the
grids using the guiding apparatus of the present invention.
FIGS. 6 (a), (b) and (c) illustrate the operative steps of the guiding
apparatus, and a method of inserting the fuel rods starting from the
bottom horizontal row of the grid cells.
DETAILED EXPLANATION OF THE PREFERRED EMBODIMENT
An embodiment of the fuel rod guiding apparatus of the present invention,
and the method of inserting fuel rods using the apparatus will be
explained with reference to FIGS. 1 to 6. In the following explanations,
the directions are referenced with respect to longitudinally extending
fuel rods. The fuel rods P1 are inserted into the assembly, in the
direction of the horizontal arrow shown in FIG. 3. The entry end is the
left end of the fuel assembly, and the entry side is likewise the side
from which the fuel enters a device or component. The vertical arrows, in
FIG. 3 indicate the direction of raising or lowering of the fuel rods to
load the fuel rods into the assembly.
FIG. 3 shows a plurality of fuel rods P1 disposed roughly horizontally on
the fuel rod base 24 of the pushout device 1C, to produce a fuel assembly
supported by a plurality of grids 10 with the driving mechanism 1B along
side the guiding apparatus of the present invention. Each grid 10 is
provided with a guiding apparatus of the same construction. The guiding
apparatus, as shown in FIGS. 1 and 2, comprises: a guiding mechanism 1A
which is disposed at the entry side of the opening end surface 10s of the
grid 10; and driving mechanism 1B, for driving the guiding mechanism 1A,
which is disposed on the outer vertical periphery of the grid 10.
The guiding mechanism 1A will be explained in further detail below with
reference to FIG. 4. The guiding mechanism 1A comprises a comb-shaped
section 2 and a side wall plate 4. The comb-shaped section 2 comprises: an
elongated part 2 disposed in contact with or adjacent to one edge part of
the strap 11x which forms a side wall of the grid cell 15; and a plurality
of dividing parts 2b disposed in contact with or adjacent to the edges of
the strap 11y which forms another side walls of the grid cell 15. The
dividing parts 2b extend from the elongated part 2a to about the same
distance as the width of the opening of the grid cell 15. The terminal
ends of the dividing parts 2b have a cut out section which protrudes out
slightly towards the entry side of the opening end surface 10s of the grid
cell 15. In the meanwhile, the side wall plate 4 is constructed so that a
plurality of regularly spaced slits are provided in the width direction of
the grid cells 15. The side wall plate 4 is attached to the comb-shaped
section 2b by engaging the slits with the protruded parts of the dividing
part 2b, thereby forming roughly square guiding spaces C, in parallel to
the opening end surface 10s, superimposed on a row of horizontally
arranged grid cells 15.
The roughly square guiding spaces C are, therefore, also defined by the
three walls of the comb-shaped section 2, i.e. the elongated part 2a, a
pair of opposed dividing parts 2b, and by the side wall plate 4. Each of
the four walls, i.e. the elongated part 2a, the pair of opposed dividing
parts 2b and the side wall plate 4, are provided with a guiding strip 3.
The guiding strips 3 extend in the exit direction of the fuel rod P1, as
shown also in FIG. 5. The guiding strips 3 slide over the spring 12 and
the dimples 13 which are formed on the surface of the straps 11x, 11y. The
straps 3 are present temporarily between the fuel rod P1 and the springs
12/dimples 13 while the fuel rods P1 are being inserted into the grid
cells 15.
Therefore, the guiding strips 3 should be as thin as allowable to permit
being inserted horizontally into or withdrawn from the grid cells 15, by
remaining straight during the insertion process. Therefore, the guiding
strips 3 should have some toughness and elasticity, and can be made of a
stainless steel thin strip of about 0.05 mm thickness, for example. To
reduce friction between the fuel rod P1 and the guiding strip 3 and to
prevent the formation of scratches, the surface of the guiding strips 3 is
coated with a resin film, nitrocellulose for example, of about 0.05 mm
thickness.
The guiding strip 3 is in a long strip form, and is applied to the
comb-shaped part 2b by being folded in half longitudinally, and bonded to
both side walls of the comb-shaped part 2b. The attachment of the guiding
strip 3 to the elongated part 2a and the side wall plate 4 is made by
folding one end of the guiding strip 3, engaging the fold with the end
part of the elongated part 2a and of the side wall plate 4, and is
extended at least to the surface of the wall which forms the guiding
spaces C and bonded thereto. The guiding strips 3 are provided, on the
elongated part 2a of the comb-shaped part 2 and on the side wall plate 4,
at regular intervals corresponding to the spacing of the grid cells 15. On
the dividing part 2b, the guiding strips 3 are provided in the central
region thereof.
A driving mechanism 1B for driving the guiding mechanism 1A is shown in
FIGS. 1 and 2. The driving mechanism 1B comprises: a frame body 33
surrounding the external vertical sides of the grid 10; a pair of freely
vertically movable sliding device 30A, 30B, for supporting the guiding
mechanism 1A, disposed on a pair of vertically parallel side walls of the
frame body 33.
Shown in FIGS. 1 and 2 is the frame body 33 which is attached to the base B
disposed below the grid 10 for insertion of the fuel rods P1 shown in FIG.
3. At each end of the base B in the width direction (horizontal direction
in FIG. 1) is disposed a motor drive 35, such as a servo motor, which
provides controlled direction and speed of rotation of a guide rod 38. The
motor drive 35 is connected to the bottom of each of the guide rods 38,
which may be ball screw drive, disposed parallel to the pair of vertical
side walls of the frame body 33, to rotate each of the guide rods 38 in
the same direction or in the opposite direction.
As shown in FIG. 2, the sliding device 30A comprises a retaining housing
30r, and a transfer housing 30t which moves the retaining housing 30r
forward and backwards in the longitudinal direction of the fuel rod P1.
Also, the sliding device 30B (not shown) is similarly constructed with a
retaining housing 30r and a transfer housing 30t. The transfer housing 30t
is screwed onto the guiding rod 38, and is moved vertically by the
rotation of the guiding rod 38.
Further, as shown in FIG. 1, the retaining housing 30r of the right sliding
device 30A and the retaining housing 30r of the left sliding device 30B
are each provided with an upper support 36a which supports the lateral
ends of the elongated part 2a of the comb-shaped section 2 of the guiding
mechanism 1A. These upper supports 36a are made to move vertically through
a stroke distance equal to the opening width of the grid cells 15 by a
reciprocating device 36c, such as a pneumatic cylinder, provided on each
retaining housing 30r. By this motion, the comb-shaped section 2 is able
to be separated from the side wall plate 4 enabling only the comb-shaped
section 2, and moved up independently of the side wall plate 4 to the next
line of grid cells 15.
One side of the upper supports 36a is provided with a lower support 36b
which supports one end of the side wall plate 4, and the other upper
support 36a is provided with a lower support 36d which supports the other
end of the side wall plate 4. The lower support 36d disposed on the
retaining housing 30r is disposed on the end of a pivoting shaft of a
driving motor 32, such as a servomotor. This configuration permits the
side wall plate 4 to pivot around the lower support 36d, thus allowing the
side wall plate 4 to be swung towards and away from the opening end
surface 10s. FIG. 1 is a front view of the apparatus showing the side wall
plate 4 in the loading position in which the side wall plate 4 is disposed
perpendicular to the fuel rods P1 and parallel to the comb-shaped section
2. On the other hand, FIG. 2 is a side view showing the side wall plate 4
which has been swung away from the comb-shaped section 2, and is disposed
nearly parallel to the fuel rods P1. The lower support 36d is provided
with a sheath like spacer which moves along with the swing of the side
wall plate 4, but out of the space associated with the fuel rod insertion,
so as to control the vibration of the side wall plate 4 and to prevent the
side wall plate 4 from touching the fuel rods P1.
Each retaining housing 30r having the above described construction is
connected to the transfer housing 30t via a reciprocating device (not
shown) housed in the transfer housing 30t. The movement of the
reciprocating device (not shown) provides the forward and backward
movement of the retaining housing 30r in the direction of the fuel rod P1,
thereby enabling the guiding strips 3 disposed on the comb-shaped section
2 and the side wall plate 4 to be inserted into and withdrawn out of the
grid cells 15.
When inserting the fuel rods P1 with the use of the driving mechanism 1B,
it is preferable to use fuel rod push-out device 1C shown in FIG. 3 to
save further effort. The fuel rod push-out device 1C is provided with a
roughly horizontal fuel rod base 24 and a reciprocating device 21 which
pushes the plurality of fuel rods P1 disposed thereon simultaneously
towards the grids 10.
Divider bars 23 are provided on the top surface of the fuel rod base 24 in
the width direction (perpendicular to the longitudinal direction of the
fuel rods P1) to separate and space the fuel rods P1 at the correct
distance to correspond with the spacing of the grid cells 15 of the grids
10. A fuel rod contact part 22 is provided at tip end of the cylinder rod
of the reciprocating device 21 disposed at the entry end of the fuel rod
base 24 for aligning the entry-side ends of the plurality of fuel rods P1
to enable all the fuel rods P1 in a row to be pushed out simultaneously.
The fuel rod base 24 is disposed on the framing 20 via a pneumatic
cylinder device to vertically move the fuel rods P1 to the loading
position into the grids 10 while maintaining them horizontally.
As described above, the apparatus of the present invention is used to
protect the surface of the fuel rods P1 when guiding and inserting a
plurality of fuel rods P1 into a plurality of lattice-like grid cells 15
of the grids 10 formed by a plurality of mutually orthognal straps 11x,
11y which are provided with springs 12 and dimples 13. The apparatus is
also provided with a guiding mechanism 1A and a driving mechanism 1B for
driving the guiding mechanism 1A. The guiding mechanism 1A comprises: a
comb-shaped sections 2 including an elongated part 2a; a plurality of
dividing parts 2b extending from the elongated part 2a; and a side wall
plate 4 which is engaged with the cut-out section of the dividing parts
2a; and guiding strips 3 extending longitudinally, which cover over the
surface of the straps 11x, 11y. The guiding mechanism 1A extends in the
width direction over the whole distance of a row of grid cells 15 of the
grids 10. The driving mechanism 1B is constructed so that the guiding
mechanism 1A can be made to approach towards or away from the opening end
surface 10s, independently move the comb-shaped section 2 and the side
wall plate 4 of the guiding mechanism 1A as a unit along a plane parallel
to the opening end surface 10S, as well as swing the side wall plate 4
separately around a pivot disposed at one end of the side wall plate 4.
Next, the method for inserting the fuel rods P1 into the grids 10 using the
guiding apparatus of the present invention will be explained with
reference to FIG. 6 which illustrates the operating steps for the guiding
mechanism 1A.
FIG. 6 is a view of a relevant section of the grids 10, and illustrates the
basic steps for inserting a horizontal row of fuel rods P1 into the grid
cells 15 of a square-shaped grid 10 disposed with its side surface resting
on top of the base B. In this case, the insertion process can begin either
from the top or bottom row of grid cells 15. The following illustration
refer to the case of starting from a bottom horizontal row and working
towards the top row of grid cells 15.
First, the driving mechanism 1B is operated to bring the guiding mechanism
1A in line with the bottom row of the grid cells 15 of the grid 10. The
reciprocating device (not shown) housed in the transfer housing 30t of the
sliding mechanism 30A, 30B is advanced, and each retaining housing 30r is
separated from the transfer housing 30t. The driving motor 32 disposed on
the retaining housing 30r is rotated, the reciprocating device 36c of the
retaining housing 30r is retracted, and the side wall plate 4 is engaged
with the dividing part 2b of the comb-shaped section 2 of the guiding
mechanism 1A.
FIG. 6 (a) is a front view of the driving mechanism 1A which is positioned
in front of the grid 10 with a small spacing. The guiding spaces C of the
driving mechanism 1A defined by the comb-shaped section 2 and the side
wall plate 4 engaged therewith are shown in bold line and is superimposed
on the grid cells 15 shown in fine line. As shown in FIG. 6 (a), the
elongated part 2a of the comb-shaped section 2 is aligned with the
horizontal top strap 11x, and the dividing part 2b is aligned with the
vertical straps 11y, and the side wall plate 4 inserted into the
protruding part of the dividing part 2b is aligned with the bottom
horizontal strap 11y.
Next, by retracting the transfer housing 30t of the sliding device 30A and
30B, the initially separated retaining housing 30r is disposed in contact
with the transfer housing 30t, and the guiding spaces C are brought close
to the opening end surface 10s of the grid 10. In this condition, the
extending guiding strips 3 which are provided on the elongated part 2a, on
the dividing parts 2b and on the side wall plate 4 become inserted into
the corresponding oppositely disposed grid cells 15. This condition is
illustrated in FIG. 5, which is a plan view of the driving mechanism 1A
adjoining the grid 10 in which three fuel rods P1 have been inserted. It
can be seen that the guiding strips 3 extending into the grid 10 intervene
between the fuel rods P1 and the springs 12/dimples 13, thereby protecting
the surface of the fuel rods P1 from possible scratches caused by their
sliding directly over the springs 12 and dimples 13.
In the meanwhile, a number of fuel rods P1 which are required to fill the
number of grid cells in a horizontal row are readied on the fuel rod base
24 of the push-out device 1C. Next, the fuel rod base 24 is raised so as
to align the fuel rods P1 with the grid cells 15, and the reciprocating
device 21 is operated to simultaneously push the fuel rods P1 on the fuel
rod base 24 into the grid cells 15.
FIG. 6 (b) shows the condition of a row of grid cells 15 after the fuel
rods P1 have been inserted thereinto through the guiding spaces C of the
guiding mechanism 1A. In this case, because the surface of the fuel rods
P1 is protected by the guiding strips 3 disposed over the springs 12 and
the dimples 13, a certain force is all that is required initially to
insert the fuel rods P1 into the grid cells 15. Furthermore, because of
the presence of the guiding strips 3, the surface of the fuel rods P1 is
protected from potential scratches caused by the fuel rods P1 sliding
directly on the springs 12 and dimples 13.
After having inserted a row of fuel rods P1 into the bottom row of grid
cells 15, the retaining housing 30r and the reciprocating device housed in
the transfer housing 30t are advanced. Then, the entire retaining housing
30r moves back longitudinally away from the grid 10. By this step, all the
guiding strips 3 which are present between the fuel rods P1 and springs
12/dimples 13 are simultaneously withdrawn from the grid cells 15. Because
the surfaces of the guiding strips 3 are covered with a sheet material of
low frictional resistance such as a resin film, it is possible to withdraw
the guiding strips 3 simultaneously and easily from the grid cells 15.
Next, the reciprocating device 36c provided on each of the retaining
housing 30r is operated (extended) to lift the retaining housing 30r,
thereby also raising the entire comb-shaped section 2 supported by the
upper support parts 36a in a parallel orientation to the side wall plate 4
and along the plane parallel to the opening end surface 10s. The
engagement between the comb-shaped section 2 and the side wall plate 4 is
thus temporarily severed.
In this condition, the comb-shaped section 2 disengaged from the side wall
plate 4 is able to be lifted to the next row of grid cells 15 above since
there is no fuel rods P1 obstructing its path. However, the side wall
plate 4 is disposed below the fuel rods P1 which have just been inserted
into the bottom row of grid cells 15, and present a barrier to the
vertical movement of the side wall plate 4. At this time, the driving
motor 32 disposed on the retaining housing 30r is operated to swing the
side wall plate 4, with the pivot at the lower support part 36d, away from
the grid 10 so as to place the side wall plate 4 roughly parallel to the
fuel rods P1. Next, the motor drives 35 provided on both sides of the base
B are operated, thereby rotating the guiding rod 38 in one direction and
driving the transfer housing 30t engaged with the ball screw guiding rod
38, thereby raising the retaining housing 30r. The new position of the
comb-shaped section 2 and the side wall plate 4 is shown in FIG. 6 (c).
Since the side wall plate 4 is out of the way by being rotated to the side
of the grid 10, the guiding apparatus can now be moved upwards without
interference from the fuel rods P1 which are inserted in the bottom row of
grid cells 15.
After moving the comb-shaped section 2 and the side wall plate 4 into the
next row of grid cells 15 above, the driving motor 32 is rotated in the
opposite direction to that in the previous step, and the side wall plate 4
is rotated back by pivoting around the lower support part 36d to the
region roughly parallel to the opening end surface 10s. The advanced (
extended ) reciprocating device 36c is retracted (contracted), thereby
reinserting the dividing parts 2b of the comb-shaped section 2 into the
slits of the side wall plate 4. The guiding spaces C to correspond with
the row of grid cells 15 are now formed above the grid cells 15 into which
the fuel rods P1 can be inserted. Another row of fuel rods P1 are then
readied on the fuel rod base 24 of push-out device 1C, and the fuel rod
base 24 is raised to align the fuel rod P1 with the new rows of grid cells
15.
The process of loading the fuel rods P1 is repeated by disposing the
guiding mechanism 1A close to the grid 10 as before, and simultaneously
inserting the fuel rods P1 into the grid cells 15 as before, thereby
enabling to load the fuel rods P1 rapidly into all the Grid cells
requiring fuel rods P1.
The method of loading the fuel rods P1 into a fuel assembly, using the
loading apparatus according to the present invention has thus been
demonstrated. In summary, the apparatus is used to insert fuel rods P1
into a plurality of grids 10 each having a plurality of latticed network
of grid cells 15 formed by assembling a plurality of straps 11x, 11y
provided with springs 12 and dimples 13. The guiding apparatus 1A
comprises: a comb-shaped section 2 having a plurality of elongated parts
2a extending along the straps 11x, and the dividing parts 2b, of a length
about equal to the opening width of the grid cells 15, extending along the
straps 11y; the side wall plate 4 which is engaged with the open end of
the dividing part 2b; and a plurality of guiding strips 3 which extend in
the direction of the fuel rods P1 disposed so as to cover the surfaces of
the straps 11x, 11y. The loading comprises the following essential steps:
(A) forming guiding spaces C to correspond with the grid cells 15 by
engaging the side wall plate 4 with the comb-shaped section 2, and
disposing said guiding spaces C adjacent to an opening end surface 10s of
said grid 10;
(B) inserting the guiding strips 3 into a horizontal row of grid cells 15
by advancing the guiding mechanism 1A in the direction of the fuel rods
P1;
(C) inserting a plurality of fuel rods P1 into the guiding spaces C formed
by the guiding mechanism 1A;
(D) withdrawing the guiding mechanism 1A in the direction of the fuel rods
P1 so as to remove the guiding strips 3 from the row of grid cells 15;
(E) raising the comb-shaped section 2 of the guiding mechanism 1A in
parallel with the opening end surface 10s of the grid 10, and in a
parallel orientation to the side wall plate 4;
(F) rotating the side wall plate 4 of the guiding mechanism 1A to a region
free from mechanical interference with the fuel rods P1;
(G) transferring the comb-shaped section 2 and the side wall plate to
another horizontal row, and repeating the above steps A to G until all the
fuel rods are inserted into the required grid cells of the assembly.
According to the method of inserting the fuel rod P1 using the apparatus
and the method of the present invention, the fuel rods P1 are in sliding
contact with the guiding strip of a sheet form disposed between the fuel
rod P1 and the springs 12/dimples 13, thereby positively preventing the
formation of scratches on the surface of the fuel rods P1. Further, the
fuel rods P1 can be inserted easily without the need for successively
deactivating the springs 12 provided on the straps 11x, 11y. The guiding
spaces C are created in a row to correspond with a row of grid cells 15
automatically and simultaneously for each of the grids 10 in an assembly,
thereby enabling to perform efficient insertion operation for assembling
the fuel rod P1.
In the embodiment presented the side wall plate 4 was disposed at the
bottom so as to enable the fuel rods P1 to be charged into the assembly
from the bottom row. It is obvious that the loading process can be
performed equally efficiently by starting from the top row. In such a
case, the guiding apparatus is inverted so that the side wall plate 4
become the top side wall plate, and the disengaged comb-shaped section 2
is lowered to the successive rows below the starting row. Many other
variation of the basic designs are possible without deviating from the
basic design concept of the present invention, and the present invention
is limited only the claims which follow.
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